1. Field of the Invention
The present invention relates to a digital cable system and method for protecting a secure micro (SM) client, and more particularly, to a digital cable system and method for protecting an SM program that can improve the security of an SM program through authentication of a host and integrity verification of the SM program.
This work was supported by the IT R&D program of MIC/IITA. [2007-S-007-01, The Development of Downloadable Conditional Access System]
2. Description of Related Art
A Conditional Access System (CAS) is a system that can insert codes to a paid broadcast program and thereby can assign only allowed subscribers with a right to view the paid broadcast program. Currently, in order to provide a paid broadcasting service, digital cable broadcasting generally uses a smart card or a cable card in a Personal Computer Memory Card International Association (PCMCIA) card type depending on an embodiment type of Conditional Access (CA) application. However, since the conventional CAS distributes CAS software or CAS client images offline using the smart card or the PCMCIA card, a predetermined period of time may be spent to reissue a card when a defect occurs in the CAS. Therefore, it may be difficult to quickly cope with the defect and the re-issuance of the card may cause additional costs.
In order to overcome the above problems, development of Downloadable Conditional Access System (DCAS) technology based on a bidirectional cable communication network currently becomes an issue. According to the conventional art, a CAS provider may install predetermined CAS software in the smart card or the PCMCIA card to thereby provide the paid broadcasting service. However, the DCAS technology may install a secure micro (SM) that can be installed with CAS software to thereby readily update an SM program via the bidirectional cable communication network when a defect occurs in the SM program including the CAS software, or when updating a version of the SM program.
If there is no guarantee for secure authorization of a subscriber, a high level of security with respect to a channel to send client software, and prevention of forgery and modulation of a host, for example, a subscriber set-top box, downloading of the SM program of the DCAS may bring serious damage, such as leakage of key technology of the SM program by malicious hacking, due to vulnerability of a wired software transmission scheme in an aspect of security.